Section 327IAC8-2.5-14. Reduced monitoring; stage 2 disinfection byproducts requirements

   (a) A PWS may reduce monitoring for stage 2 disinfection byproducts to the monitoring frequency specified in the following table if the following are met:

(1) The following analytical results:

(A) The LRAA is:

(i) less than or equal to forty-thousandths (0.040) milligrams per liter (mg/L) for TTHM; and

(ii) less than or equal to thirty-thousandths (0.030) mg/L for HAA5;

at all monitoring locations.

(B) The source water annual average TOC level before any treatment must be less than or equal to four and zero-tenths (4.0) mg/L at each treatment plant treating:

(i) surface water; or

(ii) ground water under the direct influence of surface water;

based on monitoring conducted under either section 6(b)(1)(C) or 6(d) of this rule.

(2) Only data results collected under sections 11 through 13 of this rule, this section, and sections 15 through 18 of this rule may be used to qualify for reduced monitoring.

(3) The reduced monitoring frequency levels and location requirements are specified by system size in Table 14 as follows:

Table 14

Source Water Type	Population Size Category	Monitoring Frequency1	Distribution System Monitoring Location per Monitoring Period
Subpart H	< 500		Monitoring cannot be reduced.
	500-3,300	per year	One (1) TTHM and one (1) HAA5 sample; one (1) at the location and during the quarter with the highest TTHM single measurement; one (1) at the location and during the quarter with the highest HAA5 single measurement; one (1) dual sample set per year if the highest TTHM and HAA5 measurements occurred at the same location and quarter.
	3,301-9,999	per year	Two (2) dual sample sets; one (1) at the location and during the quarter with the highest TTHM single measurement; one (1) at the location and during the quarter with the highest HAA5 single measurement.
	10,000-49,999	per quarter	Two (2) dual sample sets at the locations with the highest TTHM and highest HAA5 LRAAs.
	50,000-249,999	per quarter	Four (4) dual sample sets at the locations with the two (2) highest TTHM and two (2) highest HAA5 LRAAs.
	250,000-999,999	per quarter	Six (6) dual sample sets at the locations with the three (3) highest TTHM and three (3) highest HAA5 LRAAs.
	1,000,000-4,999,999	per quarter	Eight (8) dual sample sets at the locations with the four (4) highest TTHM and four (4) highest HAA5 LRAAs.
	≥5,000,000	per quarter	Ten (10) dual sample sets at the locations with the five (5) highest TTHM and five (5) highest HAA5 LRAAs.
Ground water	< 500	every third year	One (1) TTHM and one (1) HAA5 sample; one (1) at the location and during the quarter with the highest TTHM single measurement; one (1) at the location and during the quarter with the highest HAA5 single measurement; one (1) dual sample set per year if the highest TTHM and HAA5 measurements occurred at the same location and quarter.
	500-9,999	per year	One (1) TTHM and one (1) HAA5 sample; one (1) at the location and during the quarter with the highest TTHM single measurement; one (1) at the location and during the quarter with the highest HAA5 single measurement; one (1) dual sample set per year if the highest TTHM and HAA5 measurements occurred at the same location and quarter.
	10,000-99,999	per year	Two (2) dual sample sets; one (1) at the location and during the quarter with the highest TTHM single measurement; one (1) at the location and during the quarter with the highest HAA5 single measurement.
	100,000-499,999	per quarter	Two (2) dual sample sets at the locations with the highest TTHM and highest HAA5 LRAAs.
	≥ 500,000	per quarter	Four (4) dual sample sets at the locations with the two (2) highest TTHM and two (2) highest HAA5 LRAAs.

¹Systems on quarterly monitoring must take dual sample sets every ninety (90) days.

  (b) A PWS may remain on reduced monitoring if the following requirements, as applicable, are met:

(1) A PWS monitoring quarterly may remain on reduced monitoring as long as the:

(A) TTHM LRAA remains less than or equal to forty-thousandths (0.040) mg/L; and

(B) HAA5 LRAA remains less than or equal to thirty-thousandths (0.030) mg/L;

at each monitoring location.

(2) A PWS monitoring annually or every third year may remain on reduced monitoring if each:

(A) TTHM result is less than or equal to sixty-thousandths (0.060) mg/L; and

(B) HAA5 sample is less than or equal to forty-five thousandths (0.045) mg/L.

(3) The source water annual average TOC level, before any treatment, must be less than or equal to four and zero-tenths (4.0) mg/L at each treatment plant treating:

(A) surface water; or

(B) ground water under the direct influence of surface water;

based on monitoring conducted under either section 6(b)(1)(C) or 6(d) of this rule.

  (c) A PWS shall cease reduced monitoring and resume routine monitoring under section 12 of this rule or begin increased monitoring under section 16 of this rule if one (1) or more of the following occurs:

(1) The LRAA based on quarterly monitoring at any monitoring location exceeds either:

(A) forty-thousandths (0.040) mg/L for TTHM; or

(B) thirty-thousandths (0.030) mg/L for HAA5.

(2) The annual or once every third year sample at any location exceeds either:

(A) sixty-thousandths (0.060) mg/L for TTHM; or

(B) forty-five thousandths (0.045) mg/L for HAA5.

(3) The source water annual average TOC level, before any treatment, is greater than four and zero-tenths (4.0) mg/L at any treatment plant treating:

(A) surface water; or

(B) ground water under the direct influence of surface water;

based on monitoring conducted under either section 6(b)(1)(C) or 6(d) of this rule.

  (d) The commissioner may return a PWS to routine monitoring at the commissioner's discretion. (Water Pollution Control Division; 327 IAC 8-2.5-14; filed May 7, 2010, 9:30 a.m.: 20100602-IR-327080198FRA; errata filed Jul 2, 2010, 1:12 p.m.: 20100714-IR-327100432ACA; errata filed Mar 10, 2014, 11:59 a.m.: 20140326-IR-327140070ACA)